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towlower
Section: C Library Functions (3)Updated: 2026-02-08
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NAME
towlower, towlower_l - convert a wide character to lowercaseLIBRARY
Standard C library (libc,~-lc)SYNOPSIS
#include <wctype.h> wint_t towlower(wint_t wc); wint_t towlower_l(wint_t wc, locale_t locale);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): towlower_l():
Since glibc 2.10:
_XOPEN_SOURCE >= 700
Before glibc 2.10:
_GNU_SOURCE
DESCRIPTION
The towlower() function is the wide-character equivalent of the tolower(3) function. If wc is an uppercase wide character, and there exists a lowercase equivalent in the current locale, it returns the lowercase equivalent of wc. In all other cases, wc is returned unchanged. The towlower_l() function performs the same task, but performs the conversion based on the character type information in the locale specified by locale. The behavior of towlower_l() is undefined if locale is the special locale object LC_GLOBAL_LOCALE (see duplocale(3)) or is not a valid locale object handle. The argument wc must be representable as a wchar_t and be a valid character in the locale or be the value WEOF.RETURN VALUE
If wc was convertible to lowercase, towlower() returns its lowercase equivalent; otherwise it returns wc.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| towlower() | Thread safety | MT-Safe locale |
| towlower_l() | Thread safety | MT-Safe |
STANDARDS
- towlower()
- C11, POSIX.1-2008 (XSI).
- towlower_l()
- POSIX.1-2008.
STANDARDS
- towlower()
- C99, POSIX.1-2001 (XSI). Obsolete in POSIX.1-2008 (XSI).
- towlower_l()
- glibc 2.3. POSIX.1-2008.
NOTES
The behavior of these functions depends on the LC_CTYPE category of the locale. These functions are not very appropriate for dealing with Unicode characters, because Unicode knows about three cases: upper, lower, and title case.SEE ALSO
iswlower(3), towctrans(3), towupper(3), locale(7)